This invention relates to an apparatus and a method for the introduction of molding sand, and in particular to an apparatus and a method for blowing and thereby introducing the molding sand into a mold space to mold a sand mold.
A conventional method of blowing and thereby introducing molding sand into a mold space is known wherein the molding sand in a hopper is blown and thereby introduced into the mold space by applying highly pressurized air to the molding sand. Such a method is disclosed in, for example, JP 52-20928, A and 52-20929, A. They were both assigned to the assignee of the present application and published on Feb. 17, 1977.
However, in the conventional method, if the molding-sand contains sand balls, the efficient blowing and introducing of the molding sand from the hopper may significantly worsen. Therefore, it is relatively difficult for the molding-sand to be accurately introduced into the mold space in a predetermined condition. It is advantageous to resolve the problem of the sand balls.
In the conventional method, maintenance to avoid clogging the molding sand should be frequently performed, since an outlet or nozzle that ejects the molding sand can readily be clogged with the mold sand due to the blowing and introducing of the molding sand with the highly pressurized air.
Also, there is a tendency wherein less of the molding sand is introduced into a pattern plate having a complicated pattern, in particular, one having a long recess or pocket, in a mold space.
These problems of the clogged sand and the reduced introduction of the molding sand into the pattern plate having a complicated pattern may occur even if the molding sand includes no sand balls.
Therefore, it is also advantageous to provide an apparatus and a method applicable to accurately introduce the molding sand into a flask without it being clogged with the molding sand.
One aspect of the present invention provides an apparatus for introducing molding sand into a mold space and compacting the introduced molding sand wherein the mold space is defined by a pattern plate having a pattern, a flask is disposed on the pattern plate in such a manner that it surrounds the pattern, and a filling frame is disposed on the flask. The apparatus includes a sand hopper located above the mold space. The sand hopper includes means for introducing a first airflow of compressed air at a low pressure thereinto from an upper part thereof, and a plurality of separated nozzles at a lower portion thereof for blowing and thereby introducing molding sand held therein into the mold space by the first airflow. An aeration means supplies a second airflow of compressed air at a low pressure to the molding sand in the sand hopper to fluidize it. Vertically movable, multi-segmented squeeze feet are mounted on the lower portion of the sand hopper at various locations, each of which is adjacent to a side of a nozzle, for compacting the molding sand in the mold space.
In order to mill sand balls that are contained in the fluidized molding sand within the hopper, the apparatus may include a milling means, such as a rotary cutter.
The aeration means may introduce the second airflow of compressed air at the low pressure into the sand hopper from either or both the lower inner portion of the sand hopper and the lower peripheral portion of the sand hopper.
In one embodiment of the present invention the upper surface of the pattern plate has a convex and concave profile, and a squeeze surface that is defined by all squeeze feet also has a convex and concave profile, which matches that of the pattern plate.
The low pressure of the first or second airflow of compressed air or both may be 0.05 to 0.18 MPa. Since the molding sand in the sand hopper is fluidized by the second airflow of compressed air at the low pressure, the pressure of the first airflow of compressed air, which discharges the fluidized molding sand from the nozzle, also can be low.